The Joint Effects of Physical Activity and Long-Term Exposure to Air Pollution on Cardiovascular Mortality: A Prospective Cohort Study

Abstract

Background: Studies suggest that physical activity is beneficial to human health, and long-term exposure to air pollution is harmful. Performing physical activity will inhale more air pollutants, and thus intensified the adverse health effects of air pollution. It remains unknown the risk-benefit relationship between physical activity and long-term air pollution exposure. We aimed to determine the joint effects of physical activity and long-term exposure to air pollution on cardiovascular mortality. Methods: In a large prospective population-based cohort study, we followed up a total of 66,820 participants who aged 65 years or older from enrolment (1998-2001) to December 2011 in Hong Kong. Physical activity was reported when participants enrolled into the cohort. Concentrations of fine particulate matter (PM2.5) were estimated at residential addresses of participants at baseline. We used Cox proportional hazards regression to examine the associations of physical activity and/or long-term exposure to air pollution with cardiovascular mortality. Findings: We identified 4,749 cardiovascular deaths during a median of 11 years of follow-up. The traditional Chinese exercise (e.g., Tai Chi) and aerobic exercise were significantly reduced the risk of cardiovascular mortality. We found risk of cardiovascular mortality was negatively associated with the intensity of physical activity and positively associated with long-term exposure to PM2.5. The beneficial of physical activity on cardiovascular mortality was consistent irrespective of levels of PM2.5 concentration ( 37.2 μg/m3) where participants resided in. Interpretation: Negative association between physical activity and cardiovascular mortality did not moderated by air pollution level of the physical activity environment. The long-term benefits of physical activity on cardiovascular mortality outweighed the detrimental effects of long-term exposure to air pollution. Physical activity is recommended for people residing in relatively more polluted urban areas as well. Funding: None. Declaration of Interest: We declare no competing interests. Ethical Approval: Ethics approval was obtained from the Ethics Committee of the Faculty of Medicine, The University of Hong Kong and of the Department of Health of Hong Kong.